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Environmental accounting of Salzgitter Flachstahl products

30.08.17 | Article of Salzgitter Mannesmann Forschung

Environmental accounting, also called life cycle assessment (LCA), is a tool for evaluating the environmental compatibility of products and processes. Salzgitter Flachstahl has been collecting primary data from its steel production and conducting life cycle assessments for roughly 10 years.  With the conclusion of a joint project conducted by the German-speaking steel industry, Salzgitter Flachstahl has verified LCA data sets for flat rolled steel products with varying degrees of vertical integration.

Environmental accounting – an overview

Life cycle assessments involve a systematic analysis of the environmental impacts of products using a comprehensive view that covers all material, energy and emission flows related to the products. As a rule, the reference value is “1 kg” of the steel product under consideration. Depending on the system boundary, the product evaluation takes place either across the entire life cycle (cradle-to-grave) or across one or more life cycle phases (cradle-to-gate or gate-to-gate).

Figure 1: Life cycle phases with different system boundaries in accordance with ISO 14040/44

In addition to the comprehensive, ecological product assessment, Salzgitter Flachstahl also uses life cycle assessments to compare alternative production processes.
Depending on the set targets, life cycle assessments are used, for example, for an ecological weak point analysis within individual life cycle phases (raw material production, production, utilization, etc.) or for the ecological comparison of different material concepts for products (e.g., in cars) and their environmental impacts on the product life cycle.
Using standardized methods from the ISO 14040 /14044 series, collected primary data is used as the basis to calculate aggregated indicators in a very wide range of environmental impact categories, such as “CO2-equivalent” for the global warming potential (GWP) or “SO2 equivalent” for the acidification potential (AP). GaBi ts software from thinkstep AG is used for the necessary modeling and calculation of the environmental impact categories. This is the LCA software most commonly used in the automotive and steel industries, among others.

Participation in the VDEh LCA project

In 2016, averaged LCA data sets for steel products from the primary blast furnace route and the secondary steel route via the electric arc furnace were compiled in a joint project carried out by the VDEh (German Steel Federation) Steel Institute in cooperation with parts of the German-speaking steel industry. The project was primarily initiated in order to meet the increased customer interest in product data sets for specific regions and consequently to emphasize steel’s sustainability as a material.
Some of the companies that participated in the project were Salzgitter Flachstahl GmbH and its affiliate Peiner Träger GmbH, as well as other German-speaking steel manufacturers in the primary and secondary routes.

In the project framework, joint LCA methodology including a model was first developed for primary steel production via the integrated blast furnace route. DEKRA successfully verified the methodology, together with the generated, averaged product data sets, in accordance with ISO 14040 /14044.
In order to do justice to steel’s inherent material properties and the fact that steel products are nearly completely recyclable without quality losses and can be fed back into the primary and secondary steel production cycle in the form of scrap steel and iron (multi-recycling), in the next step a cradle-to-cradle environmental accounting study was conducted in accordance with the multi-recycling approach (MRA) developed by Prof. Finkbeiner (TU Berlin).

Figure 2 shows the development of the global warming potential of one kilogram “steel product” depending on the viewed life cycles, as determined by the MRA study. Although material losses per life cycle were taken into consideration, the closed material circuit results in significant CO2 reductions per kilogram “steel product”.

Figure 2: Results of the MRA study on the global warming potential

The product data sets developed in the project are in GaBi format. They have been used at Salzgitter Flachstahl for customer communication since early 2017.

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